| View previous topic :: View next topic |
| Author |
Message |
wan
Antenna-Theory.com Newbie
Joined: 28 Nov 2012
Posts: 4
|
 Posted: Wed Dec 12, 2012 8:48 pm Post subject: Scattering parameters (return loss) |
 |
|
Hello..
Why it must be less than -10dB? Why it does not less than -8dB or less than -12dB?
anyone plz answer this. i really need the answer.
Thank you,, |
|
| Back to top |
|
 |
Schubert
Antenna Wizard
Joined: 08 Apr 2009
Posts: 161
|
| Posted: Thu Dec 13, 2012 5:09 am Post subject: S11 (Return Loss) For An Antenna |
|
|
Who said the return loss must be less than -10 dB? That's not a rule. It sounds like a guideline.
The lower S11 is, the less mismatch loss there is. Below about -20 dB, it really doesn't matter. S11 less than -10 dB is pretty well matched, but there are products shipping with s11=-6 dB in certain industries. |
|
| Back to top |
|
|
wan
Antenna-Theory.com Newbie
Joined: 28 Nov 2012
Posts: 4
|
| Posted: Fri Dec 14, 2012 4:52 am Post subject: |
|
|
Thank you Schubert for answering my post..
Im doing a project regarding on microstrip antenna for my FYP..i read in a book n it says theoretically below -10dB is better performance..so i believe there must be a reason why it is -10dB instead of -8dB or -12dB.. |
|
| Back to top |
|
|
arka
Antenna Theory Regular
Joined: 19 Mar 2013
Posts: 10
|
| Posted: Thu Mar 21, 2013 12:37 pm Post subject: |
|
|
| wan wrote: | Thank you Schubert for answering my post..
Im doing a project regarding on microstrip antenna for my FYP..i read in a book n it says theoretically below -10dB is better performance..so i believe there must be a reason why it is -10dB instead of -8dB or -12dB.. |
Ya generally -10dB is accepted guideline. But as Schubert has mentioned it can be other than that as well.
There is nothing holy about the number 10.. It comes from the fact that S11 is nothing but the reflection coefficient... Reflection coefficient of 1/3 is generally taken as the guideline, a higher Reflection coefficient will mean more mismatch.
and in dB terms 20log10(1/3) = -9.54 dB.. that brings on to -10 dB
Thanks |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
